Hemispherotomy: efficacy and analysis of seizure recurrence

Clinical article

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Object

Hemispherotomy generally is performed in hemiparetic patients with severe, intractable epilepsy arising from one cerebral hemisphere. In this study, the authors evaluate the efficacy of hemispherotomy and present an analysis of the factors influencing seizure recurrence following the operation.

Methods

The authors performed a retrospective review of 49 patients (ages 0.2–20.5 years) who underwent functional hemispherotomy at their institution. The first 14 cases were traditional functional hemispherotomies, and included temporal lobectomy, while the latter 35 were performed using a modified periinsular technique that the authors adopted in 2003.

Results

Thirty-eight of the 49 patients (77.6%) were seizure free at the termination of the study (mean follow-up 28.6 months). Of the 11 patients who were not seizure free, all had significant improvement in seizure frequency, with 6 patients (12.2%) achieving Engel Class II outcome and 5 patients (10.2%) achieving Engel Class III. There were no cases of Engel Class IV outcome. The effect of hemispherotomy was durable over time with no significant change in Engel class over the postoperative follow-up period. There was no statistical difference in outcome between surgery types. Analysis of factors contributing to seizure recurrence after hemispherotomy revealed no statistically significant predictors of treatment failure, although bilateral electrographic abnormalities on the preoperative electroencephalogram demonstrated a trend toward a worse outcome.

Conclusions

In the present study, hemispherotomy resulted in freedom from seizures in nearly 78% of patients; worthwhile improvement was demonstrated in all patients. The seizure reduction observed after hemispherotomy was durable over time, with only rare late failure. Bilateral electrographic abnormalities may be predictive of posthemispherotomy recurrent seizures.

Abbreviations used in this paper: CUSA = Cavitron ultrasonic surgical aspirator; EEG = electroencephalogram; FH = functional hemispherotomy; MCD = malformation of cortical development; PIH = periinsular hemispherotomy; SWS = Sturge-Weber syndrome.

Article Information

Address correspondence to: David D. Limbrick Jr., M.D., Ph.D., Department of Neurological Surgery, Washington University in St. Louis, St. Louis Children's Hospital, One Children's Place, St. Louis, Missouri 63110-1077. email: limbrickd@nsurg.wustl.edu.

© AANS, except where prohibited by US copyright law.

Headings

Figures

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    Schematic representations of the 2 hemispherotomy techniques used in the current study. Left: A surface rendering showing the area resected in FH. Below are coronal and axial views showing the areas transected for the disconnection. Note that the anterior temporal lobe has been resected and the insular cortex remains intact (although this was resected in 4 of 14 cases). Right: The surface rendering the limited area of frontal and temporal opercula removed to permit the hemispheric disconnection in PIH. Coronal and axial views illustrate the disconnection. For the PIH, the corpus callosotomy is performed by subpial aspiration following the anterior cerebral arteries. A selective amygdalohippocampectomy is performed rather than a temporal lobectomy.

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    Pre- and postoperative MR images obtained in a 7-year-old boy who underwent a modified PIH on the left side. A–C: Preoperative axial, coronal, and left parasagittal contrast-enhanced T1-weighted images demonstrating left cerebral atrophy with ex vacuo dilation of the left lateral ventricle and prominent subarachnoid spaces. D–F: Postoperative MPRAGE T1-weighted images. The axial image (D) shows resection of the frontal and temporal opercula with disconnection to the midline. Solid arrow indicates the mesial occipital disconnection and provides reference for the intraoperative photograph in Fig. 4D. Coronal view (E) demonstrates the transventricular corpus callosotomy (arrowhead). Arrowhead is also seen in intraoperative photograph Fig. 4B. The left parasagittal view (F) shows the frontobasal disconnection, which is performed by subpial aspiration along the proximal anterior cerebral artery. The asterisk in this panel corresponds to the intraoperative photograph in Fig. 5A.

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    Intraoperative photographs of PIH obtained in the same boy as in Fig. 2. A: The sylvian fissure is opened widely to the level of the insula with dissection of the circular sulcus underlying the frontal and temporal opercula. B: The frontal and temporal opercula are resected, exposing the insula with overlying middle cerebral artery branches. C: Stealth neuronavigation is used to choose the most appropriate entry point into the ventricle. The ventricle is shown partially opened. The remainder of the ventricle is subsequently opened following the C-shape of the ventricle from the anterior limit of the frontal horn to the anterior extent of the temporal horn. D: The operating microscope is used to perform a selective amygdalohippocampectomy. In this photo, the amygdala has been aspirated with a CUSA, and blunt dissection with a dissector is used to remove the hippocampus.

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    Intraoperative photographs from the same child as shown in Figs. 2 and 3. A: Doppler ultrasonography is used to locate the pericallosal artery just above the interface between the septum pellucidum (SP) and the corpus callosum (CC). B: Once the artery is located, the CUSA is used to start the corpus callosotomy via subpial aspiration down to the level of the vessel. Arrowhead corresponds to the arrowhead in panel 2E and is provided for orientation to the MR image. C: The transventricular corpus callosotomy continues posteriorly, following the course of the pericallosal artery. D: The corpus callosotomy is continued to the area of the previous hippocampal tail resection to complete the mesial occipital disconnection. Arrow corresponds to the arrow in panel 2D and is provided for orientation to this area on the MR image.

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    Intraoperative photographs from the same child as shown in Figs. 24. A: A CUSA is used to complete the frontobasal disconnection by resecting basal frontal cortex and then continuing subpial aspiration along the proximal anterior cerebral artery. Asterisk corresponds to the asterisk in panel 2F to provide orientation to this area on the MR image. B: The final stage of the operation was insular decortication.

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    Pie graph showing the causes of intractable seizures in the 49 patients who underwent hemispherotomy. Number of patients for each etiology is listed in parentheses. Hemimeg = hemimegalencephaly; Polymicro = polymicrogyria.

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    Bar graph showing posthemispherotomy seizure outcome by Engel class. The bars depict the percentage out of 49 patients with Engel I–II or Engel III–IV seizure outcomes after hemispherotomy. No patient had an Engel Class IV outcome.

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    Seizure reduction after hemispherotomy is shown to be durable over time. Upper: Bar graph showing the percentage of patients in Engel Classes I–II at 6, 12, 24, and > 24 months after hemispherotomy. The number of patients with data available for each time interval is listed above each bar. The drop in % Engel Class I–II outcomes observed between 24 and > 24 months was from a single late failure in a patient 71 months postoperatively. Lower: Kaplan-Meier curve depicting probability of Engel Class I–II outcome over time. Hash marks denote censored data for individual patient outcome at the last follow-up. The outcomes in 3 patients were Engel Class III in the first postoperative month, in 1 patient at 6 months, and in 1 patient at 71 months. There was no trend for Engel class to change over the course of the postoperative period (Cochran-Armitage exact trend test = 0.67).

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